This revised application is to study longitudinal factors associated with changes in risk behaviors related to transmission of HIV and other sexually transmitted diseases (STDs) among young males. We propose to use data from the National Survey of Adolescent Males, which has collected three waves of data about a nationally representative sample of young men collected over seven years. The specific aims are: (1) To describe the longitudinal changes in HIV risk behaviors among young men, across three points in time, as they age from 15 to 19 years old in 1988 to 21 to 26 years old in 1995. Also, to assess the reliability of measurement of behaviors over time. (2) To determine whether and which key life events, such as moving away to college, entering full-time employment, marrying or cohabiting, trigger transitions from safer to riskier HIV-related behaviors or vice versa. (3) To assess how life events may trigger changes in HIV risk behaviors, particularly focusing on possible mediating roles of changes in personal attitudes and normative environment. (4) To identify characteristics of teenagers that predict persistent risky HIV-related behaviors in their later years, for use in developing intervention programs. We will investigate multiple HIV risk behaviors, selected based on May and Anderson's model of HIV transmission. Our conceptual model of factors that affect long-term changes in behaviors is based on a combination of theories about adolescent development and life course transitions to help understand the longer-term factors associated with behavioral change and social psychological theories about the roles of attitudes and perceived norms as specific, proximate determinants of behaviors.